when you have an advancement give command in a function it and it fails all the other commands to be executed in that function after that command fail.
e.g if in a function you had
say 1
advancement grant @a only story/obtain_armor
say 2
say 3

the chat would have
1
but not 2 or 3 if all the players have all ready gotten story/obtain_armor

but if other wise it would have
1
2
3
in the chat